In the Items view, we can Cut and Paste but there is no Copy command. Cut+Paste will cause a Move operation.

Optimally, I'd like to be able to "fork" an item (at least a file) by creating a new Copy/Clone of the item that shares a common history with the original item from the cloning point and backward in time, but that has its own unique history from the cloning point and forward in time. (This was possible in SVN, where it was possible to trace the history of a copied file back into the original file where it was copied from.)

That said, even if you are not going to implement a true Clone/Copy operation you could still add a Copy command in the Items view. It would then simply Add a (history-less) copy of the item when doing Paste (just as in Windows File Explorer). It would make these operations more symmetric and consistent. After all, it's a bit strange that we can Move an item inside Plastic but we need to go to the Windows File Explorer to make a simple copy of the same item...

1. Let's say the file 'foo.cs' is split via copying by somebody else on a separate branch - so I still see just 'foo.cs' on my branch. If I make commit modifications to it, then if the other person merges in my branch changes, they should get the opportunity to 'multi-merge' my changes made on 'foo.cs' into their 'foo.cs', foo2.cs', 'foo3.cs'.

2. This is a generalization of the idea of merging through file moves.

3. There should be some way of merging a split committed by somebody else into my own workspace with local uncommitted changes, similar to #1.

4. Mercurial also has this functionality. It allows a 'one-off' merge into each copy - once the merge is done though, subsequent changes to the original file are not merged in during later branch merges.